US5014232A - Adaptive digital filter having non-recursive and recursive filter elements - Google Patents

Adaptive digital filter having non-recursive and recursive filter elements Download PDF

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Publication number
US5014232A
US5014232A US07/334,712 US33471289A US5014232A US 5014232 A US5014232 A US 5014232A US 33471289 A US33471289 A US 33471289A US 5014232 A US5014232 A US 5014232A
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recursive
filtering
filter
signal
adaptive
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Tore M. Andre
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Telefonaktiebolaget LM Ericsson AB
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H21/00—Adaptive networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H21/00—Adaptive networks
    • H03H21/0012—Digital adaptive filters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
    • H04B3/23—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers
    • H04B3/237—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers using two adaptive filters, e.g. for near end and for end echo cancelling

Definitions

  • the invention relates to an adaptive, digital filter including a non-recursive part and a recursive part.
  • Uses of the filter are such as echo canceller or equalizer in telecommunication equipment.
  • the impulse response from a filter which is used for echo cancellation in telecommunication equipment shall as closely as possible immitate the impulse response of the transmission line in question. Included in the transmission line in such a case are two-wire to four-wire junctions, analogue-digital converters etc, which affect the impulse response. The latter generally has relatively long extension in time. It is therefore difficult to achieve a suitable impulse response with a filter which only has a finite impulse response.
  • filters are called non-recursive filters or FIR filters (finite impulse response).
  • FIR filters finite impulse response
  • a filter for echo cancellation should comprise both a non-recursive part and a recursive part.
  • Recursive filters are also called IIR filters (infinite impulse response).
  • the corresponding square for an IIR filter is not represented by a quadratic error surface according to the above, however, and the error surface can have local minimum points instead.
  • Known updating algorithms can fasten in such a local minimum point, resulting in that the optimum setting is never obtained.
  • Recursive filters can also be instable, as a result of that the poles in the Z transform of the transfer function can at least temporarily be moved outside the unit circle.
  • the filter coefficient can be an amount greater than one, which makes the filter instable.
  • the object of the present invention is to provide an adaptive digital filter which includes a non-recursive part and a recursive part, and which can be updated in a simple and reliable way.
  • This is achieved by the recursive part of the filter having a plurality of separate, permanently set recursive filters with different impulse responses, and in that a linear combination with adaptive weighting factors is formed by the output signals of the recursive filter.
  • the filter is updated by a single signal being utilized for updating the non-recursive part and the adaptive weighting factors in the recursive part.
  • a stable filter is also obtained in this way, due to the poles of the recursive filter not being displaced.
  • FIG. 1 illustrates a known apparatus for echo cancellation
  • FIG. 2 illustrates an example of a desired impulse response from a filter in accordance with the invention
  • FIG. 3 illustrates a first embodiment example of a filter in accordance with the invention
  • FIG. 4 illustrates a more detailed embodiment of the filter according to FIG. 3,
  • FIG. 5 is a series of graphs giving examples of different impulse responses in certain individual filters included in the filter in accordance with the invention.
  • FIG. 6 illustrates a second embodiment example of a filter in accordance with the invention.
  • FIG. 1 A known apparatus for echo cancellation is illustrated in FIG. 1.
  • a digital input signal x(n) occuring on the transmission side of telecommunication equipment is applied to a two-wire to four-wire junction 2, i.e. a hybrid, which is connected to a receiver side in the telecommunication equipment and across a two-wire line to a telephone set 4. Echo signals occur in the hybrid and in the two-wire line.
  • the output signal to the receiver side from the hybrid 2 is denoted d(n) and consists solely of echo signals when no signal is received from the telephone set 4. This signal agrees with the above-mentioned desired signal.
  • the input signal x(n) is also applied to an adaptive FIR filter 1, which generates an expected echo signal y(n).
  • An error signal e(n) is formed in summing means 3, this signal being the difference between the signals d(n) and y(n), and is utilized for updating the filter.
  • an FIR filter can be updated according to known methods, e.g. the LMS method. The impulse response of the filter is however generally too short for effective echo cancellation to be obtained.
  • FIG. 2 there is illustrated an example of a desired impulse response h(n) with relatively long extension in time, where n denotes the sequential number for the respective sample value.
  • the impulse response can be divided into two main parts. There is first a considerable transient containing the greater part of the signal energy of the impulse. There is then a long, and substantially exponentially decaying part, a so-called tail. Negative values can also occur in the impulse response.
  • FIG. 3 A first embodiment example of a filter in accordance with the invention is illustrated in FIG. 3.
  • the filter obtains a digital signal x(n) as input signal, this signal corresponding, for example, to the signal x(n) in the apparatus according to FIG. 1.
  • the input signal is applied to an FIR filter 11 directly, and to a plurality of IIR filters 13-16 after delay by a time ⁇ in a delay means 12.
  • the IIR filters are suitably of the first degree, and have permanently set filter coefficients having mutually differing values.
  • the output signal from the FIR filter 11 is supplied to a summing means 22, and the output signals from the IIR filters 13-16 are each applied to their respective multiplication means 18-21. Each of the latter has an adaptive multiplication factor. These multiplication factors are assumed to have the values W0-W3, and they are adjusted in the way given below.
  • the output signals from the FIR filter 11 and from the multiplication means 18-21 are finally added in the summing means.
  • the first part of the impulse response is generated in the FIR filter 11 and the second part is generated as a linear combination of the output signals from the IIR filters 13-16.
  • the weightings in the linear combination are here determined by the adaptive multiplication factors, or weighting factors W0-W3.
  • W0-W3 weighting factors
  • the filter output signal is denoted y(n) and is subtracted from an arbitrary desired signal d(n) in a summing means 3.
  • a difference signal e(n) thus obtained occurs on a line 17 and is utilized both for updating the non-recursive filter part, i.e. the FIR filter 11, and the recursive filter part. Updating the latter takes place by updating the adaptive weighting factors W0-W3 of the multiplication means 18-21.
  • the signals y(n), d(n) and e(n) and the summing means 3 agree with corresponding signals and means in FIG. 1, for example, but the field of application of the filter is of course not limited to echo cancellation.
  • updating means are required both for the FIR filter 11 and the multiplication means 18-21, these updating means being generally known in connection with digital filters.
  • the FIR filter 11 conventionally comprises delay means 38-40, multiplication means 34-37, and summing means 31-33.
  • the IIR filters 13-16 are of the first degree, and each has its permanently set filter coefficient. These filters are also implemented conventionally and each comprises a summing means, e.g. 131, a delay means, e.g. 132, and a multiplication means, e.g. 133.
  • the multiplication means are each allocated a permanently set coefficient P0-P3, which have mutually different values, and which are thus the filter coefficients of the IIR filters.
  • the summing means 22 in FIG. 3 is shown in FIG. 4 as a plurality of separate summing means 221-224.
  • the difference signal e(n) is used for both updating the FIR filter 11 and the adaptive weighting factors W0-W3 of the multiplication means 18-21 in the recursive filter part.
  • the problem of minimizing the difference signal e(n) is equal to minimizing the sum of the square of the expression W0 ⁇ P0 n +W1 ⁇ P1 n +W2 ⁇ P2 n +W3 ⁇ P3 n -f(n), where n goes from zero to infinity, P0-P3 are the permanent recursive filter coefficients and f(n) is the desired impulse response.
  • This sum has a quadratic error area with only one minimum, since the weighting factors are only present linearly in the expression.
  • the recursive filter part can be updated according to the same method as the non-recursive filter part, e.g. according to the LMS method.
  • the difference signal is represented by a quadratic error area, simultaneously as the difference signal represents the actual error (as opposed to an equation error structure).
  • the recursive filter part is always stable, since the poles of the individual IIR filters are not displaced. This depends in turn on that the filter coefficients P0-P3 are permanent.
  • Some graphs are illustrated in FIG. 5, and are examples of different impulse responses of the individual IIR filters in the recursive part of the filter.
  • the transfer functions of the IIR filters 13-16 are denoted in turn by h0(n)-h3(n). It is assumed that the input signal to the filters is delayed by a plurality of sample values corresponding to the length of the impulse response of the FIR filter.
  • the filter coefficients P0-P3 are, according to the example, 0.5, 0.75, 0.875 and 0.9375.
  • FIG. 6 A second embodiment example of a filter in accordance with the invention is illustrated in FIG. 6. Further to the means included in the filter according to FIG. 3, there is also a network denoted by 50 in this filter.
  • the network 50 includes multiplication means and summing means, which are adapted to form linear combinations of the output signals of the IIR filters 13-16. These means are connected such that the multiplication means 18 obtains the output signal from the filter 13 in an unaltered condition.
  • the multiplication means 19 obtains the sum of the output signal from the filter 14 and the output signal from the filter 13 multiplied by a factor, and so on, according to the Figure.
  • the linear combinations can be selected such that the input signals to the multiplications means 18, 21 will be orthogonal.
  • the filter in accordance with the invention can be used in different connections, when a relatively long impulse response is desired and not only for adaptive echo cancellation.
  • the number of IIR filters may be both more or less than just four, as illustrated in the examples.
  • the implementation of the FIR and IIR filters can also be different from what has been shown in the examples. Neither is it necessary to delay the input signal to the IIR filters. However, the delay results in that the first part of the desired impulse response is generated solely by the FIR filter, and that the second part of the response is generated solely by the recursive filter part.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Filters That Use Time-Delay Elements (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Noise Elimination (AREA)
US07/334,712 1988-06-03 1989-04-07 Adaptive digital filter having non-recursive and recursive filter elements Expired - Lifetime US5014232A (en)

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SE8802076 1988-06-03
SE8802076A SE461308B (sv) 1988-06-03 1988-06-03 Adaptivt digitalt filter omfattande en icke rekursiv del och en rekursiv del

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EP (1) EP0347394B1 (zh)
JP (1) JPH03502634A (zh)
KR (1) KR960000843B1 (zh)
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AU (1) AU609611B2 (zh)
BR (1) BR8906966A (zh)
CA (1) CA1310708C (zh)
DE (1) DE68905246T2 (zh)
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Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5159565A (en) * 1990-03-28 1992-10-27 Alcatel N.V. Method for the determination of fir filter coefficients in equalizers
US5247474A (en) * 1991-04-18 1993-09-21 Fujitsu Ten Limited Coefficients setting method of a reverberation unit
US5278552A (en) * 1989-10-23 1994-01-11 Jeco Company Limited Indicator control circuit
US5319585A (en) * 1991-11-22 1994-06-07 At&T Bell Laboratories High resolution filtering using low resolution processors
US5337264A (en) * 1992-06-01 1994-08-09 Levien Raphael L Time reversal gaussian approximation filter
US5402520A (en) * 1992-03-06 1995-03-28 Schnitta; Bonnie S. Neural network method and apparatus for retrieving signals embedded in noise and analyzing the retrieved signals
US5416799A (en) * 1992-08-10 1995-05-16 Stanford Telecommunications, Inc. Dynamically adaptive equalizer system and method
US5452289A (en) * 1993-01-08 1995-09-19 Multi-Tech Systems, Inc. Computer-based multifunction personal communications system
US5493585A (en) * 1991-04-23 1996-02-20 U.S. Philips Corporation Semi-recursive adaptive equalizer
US5535204A (en) * 1993-01-08 1996-07-09 Multi-Tech Systems, Inc. Ringdown and ringback signalling for a computer-based multifunction personal communications system
US5546395A (en) * 1993-01-08 1996-08-13 Multi-Tech Systems, Inc. Dynamic selection of compression rate for a voice compression algorithm in a voice over data modem
WO1996035259A1 (en) * 1995-05-05 1996-11-07 Unto Kalervo Laine Method of modelling the spectrum of a signal and apparatus for realizing the method
US5617423A (en) * 1993-01-08 1997-04-01 Multi-Tech Systems, Inc. Voice over data modem with selectable voice compression
US5619508A (en) * 1993-01-08 1997-04-08 Multi-Tech Systems, Inc. Dual port interface for a computer-based multifunction personal communication system
US5682386A (en) * 1994-04-19 1997-10-28 Multi-Tech Systems, Inc. Data/voice/fax compression multiplexer
US5754589A (en) * 1993-01-08 1998-05-19 Multi-Tech Systems, Inc. Noncompressed voice and data communication over modem for a computer-based multifunction personal communications system
US5757801A (en) * 1994-04-19 1998-05-26 Multi-Tech Systems, Inc. Advanced priority statistical multiplexer
US5774564A (en) * 1993-10-13 1998-06-30 Sharp Kabushiki Kaisha Active controller using lattice-type filter and active control method
US5812534A (en) * 1993-01-08 1998-09-22 Multi-Tech Systems, Inc. Voice over data conferencing for a computer-based personal communications system
US5864560A (en) * 1993-01-08 1999-01-26 Multi-Tech Systems, Inc. Method and apparatus for mode switching in a voice over data computer-based personal communications system
US5889857A (en) * 1994-12-30 1999-03-30 Matra Communication Acoustical echo canceller with sub-band filtering
US6009082A (en) * 1993-01-08 1999-12-28 Multi-Tech Systems, Inc. Computer-based multifunction personal communication system with caller ID
US6480151B2 (en) 2000-12-29 2002-11-12 Lockheed Martin Corporation GPS receiver interference nuller with no satellite signal distortion
US6504579B1 (en) * 1997-08-05 2003-01-07 Micronas Intermettal Gmbh Adaptive filter for processing video signals
US6745218B1 (en) * 1999-03-16 2004-06-01 Matsushita Electric Industrial Co., Ltd. Adaptive digital filter
US20050210091A1 (en) * 2004-03-17 2005-09-22 Ferguson Kevin M Up-sampling half-band reconstruction filtering
US6980592B1 (en) * 1999-12-23 2005-12-27 Agere Systems Inc. Digital adaptive equalizer for T1/E1 long haul transceiver
NO20053393A (no) * 2005-07-13 2006-09-11 Tandberg Telecom As Fremgangsmåte og system for ekkokansellering med liten forsinkelse.
US20070013337A1 (en) * 2005-06-29 2007-01-18 Seagate Technology Llc Adaptive voltage-mode controller for a voice coil motor
US20070052556A1 (en) * 2003-04-17 2007-03-08 Koninklijke Philips Electronics N.V. Groenewoudseweg 1 Adaptive filtering
US20090070396A1 (en) * 2006-09-29 2009-03-12 Haruka Takano Waveform equalizing device
RU198305U1 (ru) * 2020-02-26 2020-06-30 Федеральное государственное бюджетное образовательное учреждение высшего образования "МИРЭА - Российский технологический университет" Адаптивный цифровой фильтр для подавления нефлуктуационных помех

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2038904B1 (es) * 1991-09-10 1995-01-16 Alcatel Standard Electrica Procedimiento y dispositivo de cancelacion adaptativa de ecos acusticos.
US5615233A (en) * 1992-07-22 1997-03-25 Motorola, Inc. Method for channel estimation using individual adaptation
CA2145077C (en) * 1992-09-21 1998-09-01 Graham P. Eatwell Sampled-data filter with low delay
JPH0784993A (ja) * 1993-09-17 1995-03-31 Fujitsu Ltd 信号抑圧装置
FI98177C (fi) 1995-06-01 1997-04-25 Nokia Mobile Phones Ltd Menetelmä ja piirijärjestely häiriöllisen signaalin käsittelemiseksi
US7242782B1 (en) * 1998-07-31 2007-07-10 Onkyo Kk Audio signal processing circuit
US6813352B1 (en) * 1999-09-10 2004-11-02 Lucent Technologies Inc. Quadrature filter augmentation of echo canceler basis functions
DE19955596A1 (de) 1999-11-18 2001-06-13 Infineon Technologies Ag Vorrichtung und Verfahren zur Echokompensation bei Gleichlage-Übertragungsverfahren im Duplex-Betrieb über eine Zweidrahtleitung
US7079574B2 (en) 2001-01-17 2006-07-18 Radiant Networks Plc Carrier phase recovery system for adaptive burst modems and link hopping radio networks
US6628707B2 (en) 2001-05-04 2003-09-30 Radiant Networks Plc Adaptive equalizer system for short burst modems and link hopping radio networks

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2102255A (en) * 1981-05-22 1983-01-26 Int Standard Electric Corp Two-wire line for digital communication
US4495591A (en) * 1981-02-27 1985-01-22 The Regeants Of The University Of California Pipelined digital filters
US4520491A (en) * 1981-11-04 1985-05-28 Telecommunications Radioelectriques Et Telephoniques T. R. T. Transmission system using differential pulse code modulation with adaptive prediction
US4521867A (en) * 1981-08-24 1985-06-04 Victor Company Of Japan, Limited IIR digital filter having low coefficient sensitivity
US4539690A (en) * 1981-04-24 1985-09-03 Tekade Felten & Guillaume Fernmeldeanlagen Gmbh Automatic and adaptive digital nonlinear decision feedback equalizer
DE3610382A1 (de) * 1986-03-27 1987-10-01 Ant Nachrichtentech Schaltungsanordnung zur adaptiven echoloeschung in endgeraeten fuer duplex-uebertragung
EP0253583A2 (en) * 1986-07-14 1988-01-20 Oki Electric Industry Company, Limited Adaptive digital filter
US4791390A (en) * 1982-07-01 1988-12-13 Sperry Corporation MSE variable step adaptive filter
US4803647A (en) * 1986-05-30 1989-02-07 Rca Licensing Corporation Sampled data audio tone control apparatus
US4811360A (en) * 1988-01-14 1989-03-07 General Datacomm, Inc. Apparatus and method for adaptively optimizing equalization delay of data communication equipment

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5042026A (en) * 1987-03-03 1991-08-20 Nec Corporation Circuit for cancelling whole or part of a waveform using nonrecursive and recursive filters

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4495591A (en) * 1981-02-27 1985-01-22 The Regeants Of The University Of California Pipelined digital filters
US4539690A (en) * 1981-04-24 1985-09-03 Tekade Felten & Guillaume Fernmeldeanlagen Gmbh Automatic and adaptive digital nonlinear decision feedback equalizer
GB2102255A (en) * 1981-05-22 1983-01-26 Int Standard Electric Corp Two-wire line for digital communication
US4521867A (en) * 1981-08-24 1985-06-04 Victor Company Of Japan, Limited IIR digital filter having low coefficient sensitivity
US4520491A (en) * 1981-11-04 1985-05-28 Telecommunications Radioelectriques Et Telephoniques T. R. T. Transmission system using differential pulse code modulation with adaptive prediction
US4791390A (en) * 1982-07-01 1988-12-13 Sperry Corporation MSE variable step adaptive filter
DE3610382A1 (de) * 1986-03-27 1987-10-01 Ant Nachrichtentech Schaltungsanordnung zur adaptiven echoloeschung in endgeraeten fuer duplex-uebertragung
US4803647A (en) * 1986-05-30 1989-02-07 Rca Licensing Corporation Sampled data audio tone control apparatus
EP0253583A2 (en) * 1986-07-14 1988-01-20 Oki Electric Industry Company, Limited Adaptive digital filter
US4811360A (en) * 1988-01-14 1989-03-07 General Datacomm, Inc. Apparatus and method for adaptively optimizing equalization delay of data communication equipment

Cited By (55)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5278552A (en) * 1989-10-23 1994-01-11 Jeco Company Limited Indicator control circuit
US5159565A (en) * 1990-03-28 1992-10-27 Alcatel N.V. Method for the determination of fir filter coefficients in equalizers
US5247474A (en) * 1991-04-18 1993-09-21 Fujitsu Ten Limited Coefficients setting method of a reverberation unit
EP0827276A3 (en) * 1991-04-18 1998-04-22 Fujitsu Ten Limited Coefficients setting method for comb filters
US5493585A (en) * 1991-04-23 1996-02-20 U.S. Philips Corporation Semi-recursive adaptive equalizer
US5319585A (en) * 1991-11-22 1994-06-07 At&T Bell Laboratories High resolution filtering using low resolution processors
US5617513A (en) * 1992-03-06 1997-04-01 Schnitta; Bonnie S. Method for analyzing activity in a signal
US5402520A (en) * 1992-03-06 1995-03-28 Schnitta; Bonnie S. Neural network method and apparatus for retrieving signals embedded in noise and analyzing the retrieved signals
US5337264A (en) * 1992-06-01 1994-08-09 Levien Raphael L Time reversal gaussian approximation filter
US5416799A (en) * 1992-08-10 1995-05-16 Stanford Telecommunications, Inc. Dynamically adaptive equalizer system and method
US5754589A (en) * 1993-01-08 1998-05-19 Multi-Tech Systems, Inc. Noncompressed voice and data communication over modem for a computer-based multifunction personal communications system
US5815503A (en) * 1993-01-08 1998-09-29 Multi-Tech Systems, Inc. Digital simultaneous voice and data mode switching control
US5546395A (en) * 1993-01-08 1996-08-13 Multi-Tech Systems, Inc. Dynamic selection of compression rate for a voice compression algorithm in a voice over data modem
US5559793A (en) * 1993-01-08 1996-09-24 Multi-Tech Systems, Inc. Echo cancellation system and method
US6009082A (en) * 1993-01-08 1999-12-28 Multi-Tech Systems, Inc. Computer-based multifunction personal communication system with caller ID
US5574725A (en) * 1993-01-08 1996-11-12 Multi-Tech Systems, Inc. Communication method between a personal computer and communication module
US5577041A (en) * 1993-01-08 1996-11-19 Multi-Tech Systems, Inc. Method of controlling a personal communication system
US5592586A (en) * 1993-01-08 1997-01-07 Multi-Tech Systems, Inc. Voice compression system and method
US5600649A (en) * 1993-01-08 1997-02-04 Multi-Tech Systems, Inc. Digital simultaneous voice and data modem
US5617423A (en) * 1993-01-08 1997-04-01 Multi-Tech Systems, Inc. Voice over data modem with selectable voice compression
US5500859A (en) * 1993-01-08 1996-03-19 Multi-Tech Systems, Inc. Voice and data transmission system
US5619508A (en) * 1993-01-08 1997-04-08 Multi-Tech Systems, Inc. Dual port interface for a computer-based multifunction personal communication system
US5673257A (en) * 1993-01-08 1997-09-30 Multi-Tech Systems, Inc. Computer-based multifunction personal communication system
US5673268A (en) * 1993-01-08 1997-09-30 Multi-Tech Systems, Inc. Modem resistant to cellular dropouts
US5864560A (en) * 1993-01-08 1999-01-26 Multi-Tech Systems, Inc. Method and apparatus for mode switching in a voice over data computer-based personal communications system
US5471470A (en) * 1993-01-08 1995-11-28 Multi-Tech Systems, Inc. Computer-based multifunction personal communications system
US5452289A (en) * 1993-01-08 1995-09-19 Multi-Tech Systems, Inc. Computer-based multifunction personal communications system
US5535204A (en) * 1993-01-08 1996-07-09 Multi-Tech Systems, Inc. Ringdown and ringback signalling for a computer-based multifunction personal communications system
US5764627A (en) * 1993-01-08 1998-06-09 Multi-Tech Systems, Inc. Method and apparatus for a hands-free speaker phone
US5764628A (en) * 1993-01-08 1998-06-09 Muti-Tech Systemns, Inc. Dual port interface for communication between a voice-over-data system and a conventional voice system
US5812534A (en) * 1993-01-08 1998-09-22 Multi-Tech Systems, Inc. Voice over data conferencing for a computer-based personal communications system
US5790532A (en) * 1993-01-08 1998-08-04 Multi-Tech Systems, Inc. Voice over video communication system
US5774564A (en) * 1993-10-13 1998-06-30 Sharp Kabushiki Kaisha Active controller using lattice-type filter and active control method
US6570891B1 (en) 1994-04-19 2003-05-27 Multi-Tech Systems, Inc. Advanced priority statistical multiplexer
US6151333A (en) * 1994-04-19 2000-11-21 Multi-Tech Systems, Inc. Data/voice/fax compression multiplexer
US6275502B1 (en) 1994-04-19 2001-08-14 Multi-Tech Systems, Inc. Advanced priority statistical multiplexer
US5682386A (en) * 1994-04-19 1997-10-28 Multi-Tech Systems, Inc. Data/voice/fax compression multiplexer
US5757801A (en) * 1994-04-19 1998-05-26 Multi-Tech Systems, Inc. Advanced priority statistical multiplexer
US6515984B1 (en) 1994-04-19 2003-02-04 Multi-Tech Systems, Inc. Data/voice/fax compression multiplexer
US5889857A (en) * 1994-12-30 1999-03-30 Matra Communication Acoustical echo canceller with sub-band filtering
WO1996035259A1 (en) * 1995-05-05 1996-11-07 Unto Kalervo Laine Method of modelling the spectrum of a signal and apparatus for realizing the method
US6504579B1 (en) * 1997-08-05 2003-01-07 Micronas Intermettal Gmbh Adaptive filter for processing video signals
US6745218B1 (en) * 1999-03-16 2004-06-01 Matsushita Electric Industrial Co., Ltd. Adaptive digital filter
US6980592B1 (en) * 1999-12-23 2005-12-27 Agere Systems Inc. Digital adaptive equalizer for T1/E1 long haul transceiver
US6480151B2 (en) 2000-12-29 2002-11-12 Lockheed Martin Corporation GPS receiver interference nuller with no satellite signal distortion
US20070052556A1 (en) * 2003-04-17 2007-03-08 Koninklijke Philips Electronics N.V. Groenewoudseweg 1 Adaptive filtering
US7406493B2 (en) * 2004-03-17 2008-07-29 Tektronix, Inc. Up-sampling half-band reconstruction filtering
US20050210091A1 (en) * 2004-03-17 2005-09-22 Ferguson Kevin M Up-sampling half-band reconstruction filtering
US20070013337A1 (en) * 2005-06-29 2007-01-18 Seagate Technology Llc Adaptive voltage-mode controller for a voice coil motor
US7199964B2 (en) 2005-06-29 2007-04-03 Seagate Technology Llc Adaptive voltage-mode controller for a voice coil motor
NO20053393A (no) * 2005-07-13 2006-09-11 Tandberg Telecom As Fremgangsmåte og system for ekkokansellering med liten forsinkelse.
US20070071254A1 (en) * 2005-07-13 2007-03-29 Marton Trygve F Method and system for low delay echo cancelling
US7822194B2 (en) 2005-07-13 2010-10-26 Tandberg Telecom As Method and system for low delay echo cancelling
US20090070396A1 (en) * 2006-09-29 2009-03-12 Haruka Takano Waveform equalizing device
RU198305U1 (ru) * 2020-02-26 2020-06-30 Федеральное государственное бюджетное образовательное учреждение высшего образования "МИРЭА - Российский технологический университет" Адаптивный цифровой фильтр для подавления нефлуктуационных помех

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NO900357L (no) 1990-01-25
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DE68905246T2 (de) 1993-06-17
NO301203B1 (no) 1997-09-22
TR24214A (tr) 1991-07-02
DE68905246D1 (de) 1993-04-15
FI900406A0 (fi) 1990-01-25
FI93409C (sv) 1995-03-27
AU3567089A (en) 1990-01-05
CA1310708C (en) 1992-11-24
KR960000843B1 (ko) 1996-01-13
CN1038193A (zh) 1989-12-20
DK170319B1 (da) 1995-07-31
NO900357D0 (no) 1990-01-25
DK21990A (da) 1990-01-26
JPH03502634A (ja) 1991-06-13
AU609611B2 (en) 1991-05-02
KR900702646A (ko) 1990-12-08
SE8802076L (sv) 1989-12-04
GR3007321T3 (zh) 1993-07-30
FI93409B (sv) 1994-12-15
CN1014288B (zh) 1991-10-09
SE461308B (sv) 1990-01-29
SE8802076D0 (sv) 1988-06-03
BR8906966A (pt) 1990-12-18
DK21990D0 (da) 1990-01-26
MX170248B (es) 1993-08-12

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